text: Consider the example of polyethylene terephthalate (PET or "polyester"). The monomers which could be used to create this polymer are ethylene glycol and terephthalic acid:
  HO-CH-CH-OH
  and
  HOOC-CH-COOH
  In the polymer, there are two structural units, which are
  -O-CH-CH-O-
  and
  -CO-CH-CO-
  The repeat unit is
  -CH-CH-O-CO-CH-CO-O-